Militants in Nigeria have killed seven hostages, including three Westerners, in an act the British foreign secretary called “pure, cold-blooded murder.”

The seven hostages — four Lebanese and one British, one Greek and one Italian citizen – worked for the Setrapo construction company. They were kidnapped Feb 16 from Jama’are, a town about 125 miles north of Bauchi, the capital of Bauchi state. Ansaru, a group that’s an offshoot of Boko Haram, the militant Islamist movement, claimed responsibility for the killings.

“Nigeria’s police, military, domestic spy service and presidency remained silent over the killings of the construction company workers, kidnapped Feb. 16 from northern Bauchi state. The government’s silence only led to more questions about the nation’s continued inability to halt attacks that have seen hundreds killed in shootings, church bombings and an attack on the United Nations.”

In a tweet, British Foreign Secretary William Hague identified the Briton killed.

In a statement, the Italian Foreign Ministry said the Italian victim symbolized the “deepest values that unite the Italian people: the attachment to work, professionalism, tenacity, spirit of sacrifice.”

The AP also reports that Ansaru, the militant group, announced the deaths on Saturday. The BBC reported that the hostages had been killed because of a rescue attempt by British and Nigerian forces.

“Britain’s military said its warplanes which were recently spotted in Nigeria’s capital Abuja had been there to carry soldiers taking part in the French-led operation in Mali – not to rescue hostages,” the BBC reported.